How to realize image rotation using PHP and GD library

How to implement image rotation using PHP and GD libraries

Image rotation is a common image processing requirement. By rotating images, you can achieve some special effects or meet user needs. In PHP, you can use the GD library to implement the image rotation function. This article will introduce how to use PHP and the GD library to implement image rotation, with code examples.

First, make sure your PHP environment has the GD library extension installed. Enter php -m on the command line to check if there is a gd module. If not, you need to install it first.

The following is a simple code example to implement the image rotation function:

<?php
// 读取原始图片
$imagePath = 'path_to_your_image.jpg';
$sourceImage = imagecreatefromjpeg($imagePath);

// 创建一个新的画布，用于存放旋转后的图片
$width = imagesx($sourceImage);
$height = imagesy($sourceImage);
$rotateImage = imagecreatetruecolor($height, $width);

// 旋转图片
$degrees = 90; // 设置旋转的角度，可以根据需要进行更改
$rotateImage = imagerotate($sourceImage, $degrees, 0);

// 保存旋转后的图片
$outputImagePath = 'path_to_save_rotated_image.jpg';
imagejpeg($rotateImage, $outputImagePath);

// 释放资源
imagedestroy($sourceImage);
imagedestroy($rotateImage);

echo '图片旋转完成！';
?>

In the above code, the original image is first read through the imagecreatefromjpeg() function. If your image format is not JPEG, you need to use the corresponding function to read it.

Then, create a new canvas with the same size as the original image to store the rotated image. To ensure that the canvas can accommodate the rotated image, the width and height of the canvas need to be adjusted.

The next step is to implement image rotation. The imagerotate() function can be used to rotate the image according to the specified angle. Among them, the first parameter is the original image resource, the second parameter is the angle of rotation, and the third parameter is to set the background color (optional), here we set it to 0.

Finally, use the imagejpeg() function to save the rotated image to the specified path.

Finally, don’t forget to release resources and use the imagedestroy() function to destroy the original image and the rotated image.

This is just a simple example, you can modify and extend the code according to actual needs. For example, the rotation angle can be dynamically set through user input, or functions such as batch rotation of pictures can be implemented.

Summary:

This article introduces how to use PHP and GD library to achieve image rotation. By calling the functions provided by the GD library, we can easily implement the function of rotating images. I hope this article can help you when using PHP for image processing.

PHP and GD libraries are very powerful tools. Mastering them, you can implement various complex image processing operations. Not only limited to rotation, but also scaling, cropping, watermarking, and more. In actual projects, these image processing functions can bring a better user experience and enhance the attractiveness of the website.

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